Speed Freak wrote:More than one year has passed...
As the temperature is going up again I went to my garage and used the parts washing machine which I have fixed over winter
After I have cleaned the parts I took them to the company and measured it.
What should I say?
The maximum diameter measured was 56,425mm, approximately the same on all 4 cylinders.
Measured ~2-3mm below the exhaust port.
All 4 cylinders show approximately the same wear, only the one with the scatch shows slightly more wear at TDC.
At TDC where the piston rings change direction I measured ~56,403mm in direction of in/ex port and 90° to this direction ~56,405mm.
Below the exhaust ports I also measured the area where the rings change the direction at BDC.
In direction in/ex ports I measured 56,425mm and 90° rotated 56,412mm
Measured with 2 tools - mine (Mitutoyo) 0,01mm scale and the one from my company (0,001mm scale).
Both show the same result and I can repeat the measurement as often as I want.
As I mentioned in the first post, the piston clearance should be 0,06-0,065mm according to the manual.
Dimensions (out of the manual):
Standard piston diameter: 56,39-56,4mm
Standard cylinder diameter: 56,4-56,42mm
There is something wrong with the dimensions...
I`m wondering if the std. pistons really have 56,4mm at the skirt.
Would mean it`s possible to get the cylinders honed to 56,46mm and the clearance should be correct???
Anyone measured a Yamaha standard piston?
I`m thinking about buying one to measure it...
But the std. rear pistons are NLA, I only get front pistons with standard size.
I've recently grabbed up quite a few NOS Yamaha pistons for my recent RZ500 purchase. The following is what I got for measurements at the lower skirt with a 0.01mm accurate Mitutoyo micrometer. If the measurement was about between 2 lines I called it to .005mm.
Std Size Rear #1: 56.350mm
Std Size Rear #2: 56.345mm
Std Size Front #1: 56.345mm
Std Size Front #2: 56.345mm
O/S1 Rear #1: 56.640mm
O/S1 Rear #2: 56.640mm
O/S1 Rear #3: 56.640mm
O/S1 Rear #4: 56.640mm
I also measured the 2 Std TDR pistons I have:
Std TDR #1: 56.350mm
Std TDR #2: 56.345mm